Beverages and other comestibles are often processed and packaged on mechanized conveyor systems which are lubricated to reduce friction between the packaging and the load bearing surface of the conveyor. The lubricants commonly used on the load bearing surfaces of these conveyor systems, such as those used in the food processing, beverage and the brewery industries, typically contain fatty acid soaps as the active lubricating ingredient because of the superior lubricity provided by fatty acid soaps.
In addition to lubricants, conveyor systems used in the processing and packaging of comestibles are also commonly treated with an antimicrobial agent, particularly the moving portions of the conveyor system likely to carry residue of a food substance, such as the load bearing surface, in order to reduce the population of microorganisms, such as bacteria, yeast and mold, which tend to grow on the system and produce slime. Unfortunately, those antimicrobial agents found to be particularly effective for controlling microbiological populations on a conveyor system are difficult to combine with fatty acid soaps because many of these antimicrobial agents are deactivated by the anionic fatty acids.
Fatty acid soaps are known to form insoluble precipitates in the presence of cations responsible for the property of water known as hardness (Ca.sup.++, Mg.sup.++). This property of fatty acid soaps requires that water softeners and/or chemical chelating agents such as EDTA be used with lubricants based on fatty acid soaps to prevent formation of a precipitate. Failure to implement such measures generally results in the formation of a precipitate which quickly plugs the spray nozzles used for applying the lubricant to the conveyor.
Fatty acid free lubricant compositions have been developed in an effort to avoid or eliminate the precipitation problem encountered when the lubricant is diluted with water containing hardness ions. For example, Jansen, U.S. Pat. No. 4,839,067 discloses a process for the maintenance of chain-type conveyor belts by treating the conveyor belt with a lubricant composition containing a lubricating amount of a neutralized C.sub.12-18 primary fatty amine. However, as noted in Jansen, the primary fatty acid amines tend to form a precipitate in the presence of anions such as SO.sub.4.sup.-, PO.sub.4.sup.- and CO.sub.3.sup.- commonly found as impurities in water which will plug spray nozzles and soil the surfaces of the conveyor system in much the same way as fatty acid soaps in the presence of water hardness. This tendency to precipitate requires implementation of the additional step of periodically rinsing the lubricant application and conveyor system with a detergent such as an organic acid.
Hence, even though primary fatty acid amines were found to provide superior lubricity and antimicrobial activity without formation of a precipitate in the presence of hardness ions, their usefulness was compromised because of their tendency to form a precipitate in the presence of those anions commonly found in water.
Accordingly, a substantial need still exists for a conveyor lubricant which provides a combination of superior lubricity, superior antimicrobial activity and tolerance for both anions and cations commonly found in the water used to dilute the lubricant formulation prior to application to the conveyor system.